Welcome to this user forum.
I would start with a factory reset of the home hub, as the user configuration can get corrupted.
Wireless issues would be chargeable if you request a visit, and would not fix the problem.
Did you try all 13 wireless channels, including channel 13?
A visit would just be a waste of your money, as you could buy a third party router which is likely to perform better than the home hub 3, and would have external wireless aerials.
I assume you are on normal ADSL broadband?